What does this mean? Could you take the time to type a few more words so we all would have a clue as to what you are asking?
Because of the way a diesel engine works, almost always with excess air, it is possible to top up the engine with gas, be it methane (natural gas) Propane or a mixture like we get in Australia of Propane Butane and Ethane called LPG, Autogas or similar names.
As opposed to the natural gas conversions of the past that down rated the diesel to a trickle to act for ignition and fill up the engine with gas, the modern LPG/Diesel leaves the diesel fuel injection untouched and simply add a small amount of LPG to the air intake.
The result is a more complete combustion of the diesel and the added advantage of burning a cheaper fuel without interfering with the diesel side of business. THe engine can run on diesel alone or with the added boost of gas. The natural gas conversions since they down rate the diesel injection and have also to reduce the compression are only suitable for restricted operations or stationary engines.
Some of the link below provide some graphs that compare the same engine with and without LPG gas.
There are three ways to deliver the gas into the engine.
One the most basic can be done with a few dollars, rigging up a propane bottle to the air inlet, releasing a small amount of gas to the running engine. Of course the trick is to meter the gas properly or risk over fueling and damage to the engine.
This is one way to do it yourself
The same principle called 'fumigation' has been refined with the addition of computers and fancy venturi and given the name "injection" yet it is just the same as the original bottle rigged up to fancy metering systems. With the fumigation method the whole length of the admission including turbo and manifold are full of a mixture of air and LPG. When I have not heard of any unwanted explosions, the idea of a red hot turbo pushing LPG does not appeal to me, yet millions of trucks and 4wd run with them with no problems.
THe second way is to inject the gas at higher pressure than the turbo boost, directly into the manifold. This is true LPG injection and I run it on my 4wd. The LPG tank is 1/3 of the diesel tank, power gains are in the order of 30%. Fuel savings will depend on the difference in price between LPG and diesel. In OZ we pay currently $1.65 a litre for diesel and $0.60 for LPG. But even with LPG and diesel at the same price there is fuel savings because of the better combustion achieved.
The third way to deliver gas into a diesel engine is via the diesel injector. There are experimental dual injectors for diesel and Natural gas, and one company I know is trying to develop an injector for straight LPG.
-- Edited by Marc1 at 04:11, 2008-04-29